If the filing person has
previously filed a statement on Schedule 13G to report the acquisition that is the subject of this Schedule 13D, and is filing this schedule because of §§240.13d-1(e), 240.13d-1(f) or 240.13d-1(g), check the following
box. ☐

Note: Schedules filed in paper format shall include a signed original and five copies of the schedule, including all exhibits. See §240.13d-7 for
other parties to whom copies are to be sent.

*

The remainder of this cover page shall be filled out for a reporting persons initial filing on this form with respect to the subject class of securities, and for any subsequent amendment containing information
which would alter disclosures provided in a prior cover page.

The information required on the remainder of this cover page shall not be
deemed to be filed for the purpose of Section 18 of the Securities Exchange Act of 1934 (Act) or otherwise subject to the liabilities of that section of the Act but shall be subject to all other provisions of the Act
(however, see the Notes).

CUSIP No. 0001459200

13D

Page 1 of 19 Pages

1

NAMES OF
REPORTING PERSONS:

TCV VII, L.P.

2

CHECK THE APPROPRIATE BOX IF A MEMBER
OF A GROUP (SEE INSTRUCTIONS):

(a) ☐

(b) ☒

3

SEC USE ONLY:

4

SOURCE OF FUNDS (SEE
INSTRUCTIONS):

AF, OO

5

CHECK IF DISCLOSURE OF LEGAL
PROCEEDINGS IS REQUIRED PURSUANT TO ITEMS 2(d) OR 2(e):

This
Amendment No. 2 to Schedule 13D (Amendment No. 2) amends and supplements the statement on Schedule 13D filed with the United States Securities and Exchange Commission on July 2, 2015 (the Statement), relating
to the common stock, par value $0.01 per share (the Common Stock), of Alarm.com Holdings, Inc., (the Issuer). Capitalized terms used herein without definition shall have the meaning set forth in the Statement.

ITEM 4. PURPOSE OF TRANSACTION.

Item 4 of the
Statement is hereby amended and supplemented by adding the following:

On November 27, 2017, as part of an in-kind pro-rata
distribution to partners, TCV VII, TCV VII(A) and Member Fund distributed 1,308,234, 679,396 and 12,370 shares of Common Stock, respectively, to their limited partners and general partners for no consideration. The shares distributed by the TCV
Funds included 504,361 shares of Common Stock initially distributed to Management VII, of which 500,351 were subsequently distributed by Management VII to its limited partners and general partners.

Item 5 of the Statement is hereby amended and restated in its entirety as follows:

(a)  (b)

The following sets forth, as of
the date of this Schedule 13D, the aggregate number of shares of Common Stock and percentage of Common Stock beneficially owned by each of the Reporting Persons, as well as the number of shares of Common Stock as to which each Reporting Person has
the sole power to vote or to direct the vote, shared power to vote or to direct the vote, sole power to dispose or to direct the disposition, or shared power to dispose or to direct the disposition of, as of the date hereof, based on 47,140,413
shares of Common Stock outstanding as of November 1, 2017.

Reporting Person

Amountbeneficiallyowned

Percentof class

Sole powerto vote or todirect thevote

Sharedpower tovote or todirect thevote

Sole powerto dispose orto direct thedisposition

Sharedpower todispose orto directthedisposition

TCV VII

8,579,694

18.2%

8,579,694

0

8,579,694

0

TCV VII(A)

4,455,634

9.5%

4,455,634

0

4,455,634

0

Member Fund

81,123

0.2%

81,123

0

81,123

0

Management VII

13,035,328

27.7%

13,035,328

0

13,035,328

0

TCM VII

13,116,451

27.8%

13,116,451

0

13,116,451

0

Mr. Hoag

13,303,027

28.2%

186,576

13,116,451

186,576

13,116,451

Mr. Kimball

13,245,382

28.1%

128,931

13,116,451

128,931

13,116,451

Mr. Drew

13,116,451

27.8%

0

13,116,451

0

13,116,451

Mr. Reynolds

13,230,403

28.1%

113,952

13,116,451

113,952

13,116,451

Mr. Yuan

13,136,858

27.9%

20,407

13,116,451

20,407

13,116,451

Mr. Trudeau

13,116,451

27.8%

0

13,116,451

0

13,116,451

Mr. Marshall

13,149,497

27.9%

33,046

13,116,451

33,046

13,116,451

Mr. McAdam

13,157,204

27.9%

40,753

13,116,451

40,753

13,116,451

Mr. Rosenberg

13,116,451

27.8%

0

13,116,451

0

13,116,451

15

CUSIP No. 0001459200

13D

Page 16 of 19 Pages

TCV
VII, TCV VII(A) and Member Fund are the record holders of 8,579,694, 4,455,634 and 81,123 shares of Common Stock, respectively.

TCM VII,
as the ultimate general partner of TCV VII and TCV VII(A) and a general partner of Member Fund, and Management VII, as the direct general partner of TCV VII and TCV VII(A), may also be deemed to have the sole power to dispose or direct the
disposition of the shares of Common Stock held by TCV VII and TCV VII(A) and, with respect to TCM VII, certain of the shares held by Member Fund and have the sole power to direct the vote of such shares. Each of TCM VII and Management VII disclaims
beneficial ownership of the shares of Common Stock owned by TCV VII, TCV VII(A), and Member Fund except to the extent of their respective pecuniary interest therein.

Under the memorandum and articles of association of TCM VII, the Class A Directors have the shared power to dispose or direct the
disposition of the shares held by TCV VII and TCV VII(A) and certain of the shares of Common Stock held by Member Fund and the shared power to direct the vote of such shares. Each of the Class A Directors disclaims beneficial ownership of the
shares of Common Stock owned by TCM VII, Management VII, TCV VII, TCV VII(A) and Member Fund except to the extent of their respective pecuniary interest therein.

In addition, the Hoag Trust and Hamilton Investments are each the record holder of 93,288 shares of Common Stock. Mr. Hoag is a trustee
of the Hoag Trust and may be deemed to have the sole power to dispose or direct the dispositions of the shares held by the Hoag Trust. Mr. Hoag is the general partner of Hamilton Investments and may be deemed to have the sole power to dispose
or direct the dispositions of the shares held by Hamilton Investments.

Goose Rocks is the record holder of 128,931 shares of Common
Stock. Mr. Kimball is the general partner of Goose Rocks and may be deemed to have the sole power to dispose or direct the dispositions of the shares held by Goose Rocks.

The Reynolds Trust is the record holder of 113,952 shares of Common Stock. Mr. Reynolds is a trustee of the Reynolds Trust and may be
deemed to have the sole power to dispose or direct the dispositions of the shares held by the Reynolds Trust.

The Yuan Trust is the
record holder of 20,407 shares of Common Stock. Mr. Yuan is a trustee of the Yuan Trust and may be deemed to have the sole power to dispose or direct the dispositions of the shares held by the Yuan Trust.

The Marshall Trust and Marshall Partners are the record holders of 32,780 and 266 shares of Common Stock, respectively. Mr. Marshall is a
trustee of the Marshall Trust and may be deemed to have the sole power to dispose or direct the dispositions of the shares held by the Marshall Trust. Mr. Marshall is the general partner of Marshall Partners and may be deemed to have the sole
power to dispose or direct the dispositions of the shares held by Marshall Partners.

The Reporting Persons may be deemed to be acting as
a group in relation to their respective holdings in the Company but do not affirm the existence of any such group.

Except as set forth in
this Item 5(a)  (b), each of the Reporting Persons disclaims beneficial ownership of any Common Stock owned beneficially or of record by any other Reporting Person.

(c) On November 28, 2017: (i) Management VII disposed of 4,010 shares of Common Stock at prices ranging from $41.865 to $42.87 per share in a series
of open market transactions on the Nasdaq Global Select Market for a weighted average price per share of $42.4306; (ii) Mr. Trudeau disposed of 55,187 shares of Common Stock at prices ranging from $43.50 to $43.625 per share in a series of
open market transactions on the Nasdaq Global Select Market for a weighted average price per share of $43.5068; (iii) the Marshall Trust and Marshall Partners disposed of 7,234 and 266 shares of Common Stock, respectively, in each case at a
price per share of $43.50, in open market transactions on the Nasdaq Global Select Market; and (iv) the Rosenberg Trust

16

CUSIP No. 0001459200

13D

Page 17 of 19 Pages

disposed of 16,521 shares of Common Stock at prices ranging from $41.865 to $42.87 per share in a series of open market transactions on the Nasdaq Global Select Market for a weighted average
price per share of $42.5143. The Reporting Persons undertake to provide, upon request by the staff of the SEC, the Issuer, or a security holder of the Issuer, full information regarding the number of shares sold at each separate price for these
transactions.

On November 29, 2017: (i) the Drew Trust disposed of 34,232 shares of Common Stock at prices ranging from $40.62
to $42.10 per share in a series of open market transactions on the Nasdaq Global Select Market for a weighted average price per share of $41.1431; and (ii) Ten 271 Partners B disposed of 20,956 shares of Common Stock at prices ranging from
$40.62 to $42.10 per share in a series of open market transactions on the Nasdaq Global Select Market for a weighted average price per share of $41.1433. The Reporting Persons undertake to provide, upon request by the staff of the SEC, the Issuer,
or a security holder of the Issuer, full information regarding the number of shares sold at each separate price for these transactions.

Except as reported in this Item 5(c) and in Item 4, above, during the past 60 days none of the Reporting Persons or Related Persons
has effected any transactions in the Common Stock.

(d) Except as set forth herein, no other person is known to have the right to receive or the power to
direct the receipt of dividends from, or the proceeds from the sale of the Common Stock beneficially owned by the Reporting Persons.

(e) Not applicable.

17

CUSIP No. 0001459200

13D

Page 18 of 19 Pages

SIGNATURE

After reasonable inquiry and to
the best of each of the undersigneds knowledge and belief, each of the undersigned certifies that the information set forth in this statement is true, complete and correct.